Tire studs give a vehicle traction when going over ice and hard-parked snow. Tire studs are installed, for example, on an all-terrain vehicle's tires when driving in the polar ice caps.
Many patents have been issued with respect to tire studs or anti-skid devices. An early tire traction device is described, for example, in U.S. Pat. No. 2,535,299 which was issued to A. Leach et al. on Dec. 26, 1950 and is entitled "Tire Traction Cover." This patent consists of a flexible band disposed about the tire and having tire studs mounted on its outer surface. U.S. Pat. No. 2,535,299 also discloses belt straps which enable the flexible band to be strapped onto the tire. There are several shortcomings with the device of U.S. Pat. No. 2,535,299. First, the flexible band on which the tire studs are mounted must be manufactured in many sizes to account for different-sized tires, both with respect to the width of the rubber tire tread and the tire circumference. A second shortcoming is that when a stud disengages from the flexible band it is not readily possible to mount another stud to take its place. Therefore, if a group of studs, in one particular location on the flexible band disengage, then the tire would not have traction in that particular area of the traction cover and would render the entire device useless.
Another prior art device is disclosed in U.S. Pat. No. 2,627,888 which issued to A. W. Bull and includes a tire tread having an adjustable traction device. This device is similar to the device of U.S. Pat. No. 2,535,299 in that the studs are mounted by the manufacturer on a particular surface which is later connected to the tire. The only difference is that in U.S. Pat. No. 2,627,888 the surface that the studs are mounted into is the actual tire tread and in U.S. Pat. No. 2,535,299 the surface is a flexible band which is strapped over the tire tread. Just as in U.S. Pat. No. 2,535,299, there are several shortcomings with U.S. Pat. No. 2,627,888. A prime disadvantage is that the user has to unthread the anti-skid devices from the tire tread by hand, since they are embedded inside the tire tread. This is a difficult task, since the anti-skid devices are usually flush with respect to the tire tread, due to road wear of the anti-skid devices. In addition, it is often difficult to unthread these anti-skid devices when mud, dirt, or snow encapsulates them. But a main shortcoming of U.S. Pat. Nos. 2,535,299 and 2,627,888 is that they disclose anti-skid contraptions which do not allow for replacement studs once the existing studs are disengaged or damaged.
Danish Patent No. 85,665 issued to Victor Peche on Jun. 2, 1958 and discloses an individual anti-skid device which is embedded in the rubber tire tread of a vehicle's tire. A shortcoming of this device is that the portion which is embedded into the tire tread resembles a tiny spike. The part of the anti-skid device which protrudes out of the anti-skid device is a conical head which is barely attached to the spike portion. Perpetual tire rotation could cause the device to rip out of the rubber tire tread, and could also tear the conical head from the spike portion, thus leaving the spike stuck in the tire tread where it plays no function.
A U.S. patent which discloses a tire traction device, whereby each individual device is separate and independent of one another was issued to W. B. Coate on Feb. 11, 1964, U.S. Pat. No. 3,120,863. U.S. Pat. No. 3,120,863 discloses a tire traction device resembling an ordinary screw which is threaded to the tire tread of a vehicle's tire. U.S. Pat. No. 3,120,863 discloses that the traction device is threaded on the sides of the tire tread and not in the front side of the tire tread. A major shortcoming of this device is that tire rotation easily rips the device out of the rubber tire tread, leaving a hole in the rubber tire tread and even possibly damaging the tire tread if the anti-skid device rips out sideways.
Both Danish Patent No. 85,665 and U.S. Pat. No. 3,120,863 disclose threaded, screw-like devices which tend to be unstable when embedded in the rubber portion of tire and tire rotation could cause them to be ripped out of the tire. These anti-skid devices rip out of the rubber tire tread primarily because the threaded portion which is embedded in the tire has a conventional pitch between threads and the rubber is thus unable to fully grip the device. In addition, the head of these devices is not configured to withstand a large amount of weight, and therefore, are not suitable for use on tires of heavy vehicles, such as military vehicles or trucks.
A threaded tire stud with a conventional pitch is prone to forming air cavities along the thread-pitch boundaries as it is embedded in a rubber tire tread. This is due to the fact that because of its elasticity characteristics, the rubber is unable to fully and intimately adhere to the entire surface of a threaded anti-skid device having a conventional pitch. The air cavities which are thus formed in the rubber tire tread cause the anti-skid device with conventional pitch to be unstable and susceptible to dislodgement.
The phenomenon which causes rubber to elastically adhere to the surface of a device which is embedded in it is called the flange effect. Therefore, a threaded anti-skid device with conventional pitch, is not fully prone to the flange effect and may easily rip out of the rubber tire tread. Further still, one may easily remove an anti-skid device which is not fully prone to the flange effect from the rubber tire tread by a simple pull. However, an anti-skid device which is completely under the influence of the flange effect requires a tool to remove, because it is strongly held in place.
In addition, there are prior art anti-skid devices which require installation using a custom-made tool, which is usually retro-fitted with pressure gauges and air pumps, to embed the anti-skid devices into the rubber tire tread. This necessitates that the anti-skid devices be embedded at a location where such custom-made tools can be found, such as in a garage or an auto repair shop. Therefore, a driver who does not have readily available access to such a custom-made tool, has no remedial recourse if he suddenly finds himself driving in icy conditions or hard-packed snow.
In view of the shortcomings of the prior art anti-skid devices, it is an object of the subject invention to provide an improved, durable, threadedly engageable, and more stable tire stud.
It is a further object of the subject invention to provide a tire stud that can be easily varied as to the length the head portion protrudes from the rubber tire tread.
It is a further object of the subject invention to provide a tire stud that is particularly effective in withstanding pressure due to the weight of the vehicle.
Still a further object of the subject invention is to provide a tire stud that is threaded in a rubber tire tread without the need of a custom-made tool.